We propose to study synaptic mechanisms of cellular interaction in the vertebrate retina. With recently developed techniques it is now possible to accurately characterize the electrical properties of retinal cells in terms of their current voltage relations. This relationship can be modified in specific ways by endogenous synaptic transmitters, and the effects can be controlled experimentally by use of generalized and specific synaptic transmission blocking agents. The nature of the reciprocal synapse at the outer plexiform layer, the mechanism of bipolar activity of opposite polarity driven presumably by a single receptor transmitter, mechanisms of propagation of signals in non-spiking cells, and special regenerative properties of retinal cell membranes will be studied with these techniques. The ultimate goal of these studies is to characterize synaptic interactions in the retina in terms of a system of specific membranes which respond to identified synaptic transmitter by modulating the flow of particular ions to control states of activity.